US5339639A - Freon free refrigerator - Google Patents
Freon free refrigerator Download PDFInfo
- Publication number
- US5339639A US5339639A US07/908,661 US90866192A US5339639A US 5339639 A US5339639 A US 5339639A US 90866192 A US90866192 A US 90866192A US 5339639 A US5339639 A US 5339639A
- Authority
- US
- United States
- Prior art keywords
- chamber
- gas
- refrigerator
- adsorbent material
- cold zone
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B15/00—Sorption machines, plants or systems, operating continuously, e.g. absorption type
- F25B15/16—Sorption machines, plants or systems, operating continuously, e.g. absorption type using desorption cycle
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B25/00—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00
- F25B25/02—Compression-sorption machines, plants, or systems
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
- F25B9/14—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the cycle used, e.g. Stirling cycle
- F25B9/145—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the cycle used, e.g. Stirling cycle pulse-tube cycle
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/14—Compression machines, plants or systems characterised by the cycle used
- F25B2309/1407—Pulse-tube cycles with pulse tube having in-line geometrical arrangements
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/14—Compression machines, plants or systems characterised by the cycle used
- F25B2309/1412—Pulse-tube cycles characterised by heat exchanger details
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/14—Compression machines, plants or systems characterised by the cycle used
- F25B2309/1417—Pulse-tube cycles without any valves in gas supply and return lines
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/14—Compression machines, plants or systems characterised by the cycle used
- F25B2309/1421—Pulse-tube cycles characterised by details not otherwise provided for
Definitions
- Refrigeration at about ambient temperature is currently achieved by using the compression cycle with halogenated hydrocarbons such as freon (Registered Trademark) gas as the refrigerating medium.
- Freon gas is compressed and the heat of compression i s conducted to atmosphere thereby causing the gas to condense to a liquid.
- the liquid freon is then passed to the inside of an insulating chamber where it is allowed to expand and evaporate thereby cooling the chamber.
- the expanded freon gas then returns to a compressor for the cycle to be repeated.
- a refrigerator comprises a chamber containing a bed of an adsorbent material and a compressible gas capable of being adsorbed under pressure by said adsorbent material and desorbed from said adsorbent material when said pressure is released, means for alternately compressing and decompressing the gas within the chamber thus creating a cold zone within the chamber, and means for thermally connecting the cold zone to a location to be refrigerated.
- FIG. 2 is a second embodiment of the refrigerator according to the present invention with a housing sealing the compressor and piston.
- the compressor 6 and piston associated therewith may be sealed within a housing 9 as shown specifically in FIG. 2.
- the compressor 6 is started and upwardly extends the piston 12 to thereby compress the carbon dioxide.
- the upward movement of the piston 12 may extend into the interior of the cylinder as shown specifically in FIG. 3. material 3 at the lower end of the zeolite bed thereby generating heat.
- the heat generated is carried upward by further incoming carbon dioxide with the result that when the compression stroke of the compressor is completed a heat spot is formed at the extreme upper end of the cylinder 2. This heat spot is dissipated by means of the cooling fins 4 to ambient atmosphere.
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Cold Air Circulating Systems And Constructional Details In Refrigerators (AREA)
- Sorption Type Refrigeration Machines (AREA)
- Separation Of Gases By Adsorption (AREA)
- Compressor (AREA)
Abstract
A refrigerator includes a cylinder containing a bed of adsorbent material and a gas, e.g. carbon dioxide. A piston compresses the gas which is adsorbed by the adsorbent material and the heat of adsorption is dissipated by fins to atmosphere. The piston, when retracted, decompresses the gas which desorbs from the adsorbent material. Repeated compression and decompression of the gas causes a cold zone to be created within the material which is thermally linked to a location to be refrigerated.
Description
The present invention relates to refrigerators.
Refrigeration at about ambient temperature is currently achieved by using the compression cycle with halogenated hydrocarbons such as freon (Registered Trademark) gas as the refrigerating medium. Freon gas is compressed and the heat of compression i s conducted to atmosphere thereby causing the gas to condense to a liquid. The liquid freon is then passed to the inside of an insulating chamber where it is allowed to expand and evaporate thereby cooling the chamber. The expanded freon gas then returns to a compressor for the cycle to be repeated.
Problems appear to arise when these known refrigerators wear out since, when they are re-cycled or scrapped, it is believed that the freon type gases are released thereby damaging the ionosphere.
An alternative cycle is available in domestic refrigeration and is known as the ammonia adsorption cycle. However, it is less efficient and often less reliable being dependent on the containment of hydrogen gas.
It is an aim of the present invention to provide a refrigerator which utilizes the cold zone(s) which are created when certain gases are adsorbed by and then desorbed from a bed of adsorbent material.
According to one aspect of the present invention, a refrigerator comprises a chamber containing a bed of an adsorbent material and a compressible gas capable of being adsorbed under pressure by said adsorbent material and desorbed from said adsorbent material when said pressure is released, means for alternately compressing and decompressing the gas within the chamber thus creating a cold zone within the chamber, and means for thermally connecting the cold zone to a location to be refrigerated.
According to a further aspect of the present invention, a method of refrigeration comprises the steps of:
a) compressing a gas within a chamber containing a bed of an adsorbent material such that some at least of the gas is adsorbed by said adsorbent material;
b) removing heat generated by the adsorption step;
c) decompressing the gas within the chamber such that the gas is desorbed from the adsorbent material thereby creating a cold zone; and
d) thermally connecting said cold zone to a location to be refrigerated.
The following drawings in which like reference characters indicate like parts are illustrative of embodiments of the invention and are not intended to limit the invention as encompassed by the claims forming part of the application.
FIG. 1 is a schematic view of one embodiment of a refrigerator according to the present invention; and
FIG. 2 is a second embodiment of the refrigerator according to the present invention with a housing sealing the compressor and piston.
FIG. 3 is a schematic view of a third embodiment of the invention showing the piston slidably received within the cylinder.
As shown in FIG. 1, a refrigerator 1 includes a chamber in the form of a hollow cylinder 2 within which is located a bed of an adsorbent material 3, for example, a zeolite having a high heat adsorption such as 13X or 5A type. Also located within the cylinder 2 is a pre-selected volume of a gaseous medium such as carbon dioxide which has a high affinity for the adsorbent material 3 and is readily compressible.
As shown in FIG. 1, the cylinder 2 is arranged vertically and operatively connected to its lower end is a piston 12 extending from a compressor 6, preferably of the type totally sealed from the atmosphere (see FIG. 2). In an embodiment of the invention as particularly shown in FIG. 3, the piston 12 is slidable received within the cylinder 2. The piston 12 is adapted to seal the carbon dioxide within the cylinder 2 and, when reciprocated, alternately to compress and decompress the carbon dioxide.
Adjacent the lower end of the cylinder 2 there is located thermally connecting means in the form of plates 7 which extend from the outer surface of the cylinder 2 to enter the interior of a compartment B which interior is to be cooled.
At its upper (as shown) end attached to the cylinder 2 are a plurality of cooling fins 4.
In accordance with a preferred embodiment of the invention, the compressor 6 and piston associated therewith may be sealed within a housing 9 as shown specifically in FIG. 2.
In use as shown in FIG. 1, the compressor 6 is started and upwardly extends the piston 12 to thereby compress the carbon dioxide. The upward movement of the piston 12 may extend into the interior of the cylinder as shown specifically in FIG. 3. material 3 at the lower end of the zeolite bed thereby generating heat. The heat generated is carried upward by further incoming carbon dioxide with the result that when the compression stroke of the compressor is completed a heat spot is formed at the extreme upper end of the cylinder 2. This heat spot is dissipated by means of the cooling fins 4 to ambient atmosphere.
During downward retractive movement of the piston 12, the decompression of the carbon dioxide takes place which carbon dioxide is desorbed from the adsorbent material 3 leading to a net cooling of the adsorbent material 3. Because some of the heat has been dissipated by means of the cooling fins 4 some of the material 3 will become very cool and it has been found, over a number of cycles of the compressor, a cold spot is formed within the bed of adsorbent material 3 close to the lower end of the cylinder 2 (at the point of entry of the piston 12 in the embodiment shown in FIG. 3). This cold spot is thermally linked to the interior of the compartment 8 by plates 7 thereby allowing the interior of the compartment 8 to be refrigerated.
Particular advantages of the embodiment described above are (a) the materials employed are all environmentally friendly so that the ultimate disposal of the refrigerator presents no problems; and (b) the system is a closed system requiring no constant replacement of adsorbent or gas.
Although the invention has been described with reference to specific example, it will be appreciated by those skilled in the art that the invention may be embodied in any other form.
Claims (11)
1. A refrigerator comprising a chamber containing a bed of an adsorbent material and a compressible gas capable of being adsorbed under pressure by said adsorbent material and desorbed from said adsorbent material when said pressure is reduced, means for alternately compressing and decompressing the gas within the chamber thus creating a cold zone within the chamber and means for thermally connecting the cold zone to a compartment to be refrigerated, said thermally connecting means comprising a plurality of conductive plates located adjacent the chamber and in alignment with the cold zone and extending within the interior of the compartment to be refrigerated.
2. A refrigerator as claimed in claim 1, in which the adsorbent material is a zeolite and the compressible gas is carbon dioxide.
3. A refrigerator as claimed in claim 1, in which at the upper end of the cylinder cooling fins are attached to the cylinder.
4. A refrigerator as claimed in claim 1 wherein the means for alternately compressing and decompressing the gas comprises a piston movable by a compressor.
5. A refrigerator as claimed in claim 4 wherein the compressor and piston are contained in a sealed housing.
6. A method of refrigeration comprising the steps of:
a) compressing a gas within a chamber containing a bed of an adsorbent material such that at least some of the gas is adsorbed by said adsorbent material;
b) removing heat generated by the adsorption step;
c) decompressing the gas within the chamber such that the gas is desorbed from the adsorbent material thereby creating a cold zone; and
d) thermally connecting said cold zone to a compartment to be refrigerated by means of a plurality of conductive plates located adjacent the chamber, said conductive plates being in alignment with the cold zone and extending within the interior of the compartment to be refrigerated.
7. A refrigerator comprising a chamber containing a bed of a zeolite and gaseous carbon dioxide capable of being adsorbed under pressure by said zeolite and desorbed from said zeolite when said pressure is reduced, means for alternately compressing and decompressing the gas within the chamber thus creating a cold zone within the chamber and means for thermally connecting the cold zone to a compartment to be refrigerated.
8. A refrigerator as claimed in claim 7 in which the thermally connecting means ia plurality of conductive plates located adjacent the chamber and in alignment with the cold zone and extending within the interior of the compartment to be refrigerated.
9. A refrigerator as claimed in claim 7 in which at the upper end of the chamber cooling fins are attached to the chamber.
10. A refrigerator as claimed in claim 7 wherein the means for alternately compressing and decompressing the gas comprises a piston movable by a compressor.
11. A refrigerator as claimed in claim 10 wherein the compressor and piston are contained in a sealed housing.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB919115140A GB9115140D0 (en) | 1991-07-13 | 1991-07-13 | Improvements in refrigerators |
GB9115140.7 | 1991-07-13 |
Publications (1)
Publication Number | Publication Date |
---|---|
US5339639A true US5339639A (en) | 1994-08-23 |
Family
ID=10698306
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US07/908,661 Expired - Fee Related US5339639A (en) | 1991-07-13 | 1992-07-02 | Freon free refrigerator |
Country Status (8)
Country | Link |
---|---|
US (1) | US5339639A (en) |
EP (1) | EP0523849B1 (en) |
JP (1) | JPH05196317A (en) |
KR (1) | KR100231932B1 (en) |
AU (1) | AU650346B2 (en) |
CA (1) | CA2072443A1 (en) |
DE (1) | DE69202412T2 (en) |
GB (1) | GB9115140D0 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5813248A (en) * | 1995-11-01 | 1998-09-29 | Zornes; David A. | Balanced adsorbent refrigerator |
US6216467B1 (en) | 1998-11-06 | 2001-04-17 | Helix Technology Corporation | Cryogenic refrigerator with a gaseous contaminant removal system |
US20130111894A1 (en) * | 2010-07-19 | 2013-05-09 | Technion Research & Development Foundation Ltd | System and method for energy conversion |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2708724B1 (en) * | 1993-07-29 | 1995-10-13 | Boye Sa Manuf Vetements Paul | Production of cold by adsorption / desorption of carbon dioxide with the use of activated carbon fibers or activated carbon as adsorbent material. |
GB9513606D0 (en) * | 1995-07-04 | 1995-09-06 | Boc Group Plc | Apparatus for chilling fluids |
WO1997014004A1 (en) * | 1995-10-06 | 1997-04-17 | Manufactures De Vetements Paul Boye S.A. | Refrigerating method and device |
DE19925646C2 (en) * | 1998-01-30 | 2001-12-20 | Eberhard Wistuba | Use of a mixture of substances for the disinfection of water and for lowering the pH value and method for cooling |
EP1711755A4 (en) * | 2004-01-28 | 2011-03-09 | Commw Scient Ind Res Org | Method, apparatus and system for transferring heat |
GB0507953D0 (en) * | 2005-04-21 | 2005-05-25 | Thermal Energy Systems Ltd | Heat pump |
CN105333640B (en) * | 2015-06-29 | 2017-09-22 | 河南农业大学 | A kind of shell-tube type adsorbent bed with acanthopore diaphragm type adsorbate pipe |
CN112833580B (en) * | 2021-01-20 | 2022-07-15 | 重庆科技学院 | Industrial waste heat and residual pressure comprehensive recovery system |
Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3262277A (en) * | 1965-02-02 | 1966-07-26 | Gen Electric | Low temperature thermal regenerator |
GB1078107A (en) * | 1963-12-12 | 1967-08-02 | Comp Generale Electricite | Cooling apparatus |
US3817044A (en) * | 1973-04-04 | 1974-06-18 | Philips Corp | Pulse tube refrigerator |
US4183734A (en) * | 1977-06-01 | 1980-01-15 | Cjb Developments Limited | Adsorption heat pump |
US4413670A (en) * | 1980-05-30 | 1983-11-08 | Studiengesellschaft Kohle Mbh | Process for the energy-saving recovery of useful or available heat from the environment or from waste heat |
US4489533A (en) * | 1982-12-06 | 1984-12-25 | Hobart Corporation | Package handling in a film wrapping machine |
US4584840A (en) * | 1983-06-20 | 1986-04-29 | Sulzer Brothers Limited | Cooling machine or heat pump |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4489553A (en) * | 1981-08-14 | 1984-12-25 | The United States Of America As Represented By The United States Department Of Energy | Intrinsically irreversible heat engine |
-
1991
- 1991-07-13 GB GB919115140A patent/GB9115140D0/en active Pending
-
1992
- 1992-06-12 EP EP92305408A patent/EP0523849B1/en not_active Expired - Lifetime
- 1992-06-12 DE DE69202412T patent/DE69202412T2/en not_active Expired - Fee Related
- 1992-06-23 AU AU18490/92A patent/AU650346B2/en not_active Ceased
- 1992-06-26 CA CA002072443A patent/CA2072443A1/en not_active Abandoned
- 1992-07-02 US US07/908,661 patent/US5339639A/en not_active Expired - Fee Related
- 1992-07-11 KR KR1019920012381A patent/KR100231932B1/en not_active IP Right Cessation
- 1992-07-13 JP JP4185388A patent/JPH05196317A/en active Pending
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1078107A (en) * | 1963-12-12 | 1967-08-02 | Comp Generale Electricite | Cooling apparatus |
US3262277A (en) * | 1965-02-02 | 1966-07-26 | Gen Electric | Low temperature thermal regenerator |
US3817044A (en) * | 1973-04-04 | 1974-06-18 | Philips Corp | Pulse tube refrigerator |
US4183734A (en) * | 1977-06-01 | 1980-01-15 | Cjb Developments Limited | Adsorption heat pump |
US4413670A (en) * | 1980-05-30 | 1983-11-08 | Studiengesellschaft Kohle Mbh | Process for the energy-saving recovery of useful or available heat from the environment or from waste heat |
US4489533A (en) * | 1982-12-06 | 1984-12-25 | Hobart Corporation | Package handling in a film wrapping machine |
US4584840A (en) * | 1983-06-20 | 1986-04-29 | Sulzer Brothers Limited | Cooling machine or heat pump |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5813248A (en) * | 1995-11-01 | 1998-09-29 | Zornes; David A. | Balanced adsorbent refrigerator |
US6216467B1 (en) | 1998-11-06 | 2001-04-17 | Helix Technology Corporation | Cryogenic refrigerator with a gaseous contaminant removal system |
US20130111894A1 (en) * | 2010-07-19 | 2013-05-09 | Technion Research & Development Foundation Ltd | System and method for energy conversion |
US9562522B2 (en) * | 2010-07-19 | 2017-02-07 | Technion Research & Development Foundation Limited | System and method for energy conversion by pressure wave and/or phase-exchange |
US10683852B2 (en) | 2010-07-19 | 2020-06-16 | Technion Research & Development Foundation Limited | System and method for energy conversion |
Also Published As
Publication number | Publication date |
---|---|
AU650346B2 (en) | 1994-06-16 |
KR930002770A (en) | 1993-02-23 |
JPH05196317A (en) | 1993-08-06 |
DE69202412T2 (en) | 1995-09-14 |
CA2072443A1 (en) | 1993-01-14 |
EP0523849A1 (en) | 1993-01-20 |
KR100231932B1 (en) | 1999-12-01 |
DE69202412D1 (en) | 1995-06-14 |
AU1849092A (en) | 1993-01-14 |
EP0523849B1 (en) | 1995-05-10 |
GB9115140D0 (en) | 1991-08-28 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: BOC GROUP PLC, THE Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:GARRETT, MICHAEL ERNEST;REEL/FRAME:007000/0496 Effective date: 19940518 |
|
FEPP | Fee payment procedure |
Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
FPAY | Fee payment |
Year of fee payment: 4 |
|
REMI | Maintenance fee reminder mailed | ||
LAPS | Lapse for failure to pay maintenance fees | ||
STCH | Information on status: patent discontinuation |
Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 |
|
FP | Lapsed due to failure to pay maintenance fee |
Effective date: 20020823 |